Being able to smoothly ramp exposures during a timelapse is crucial to capturing lengthy shots of sunrises / sunsets, and also for successfully capturing the elusive "holy grail" of shooting from day into night or vise versa.
Today, there many options out on the market for bulb-ramping, done by USB control of Canon and even other cameras. This is the first in a series of tutorials in which I will be showing you how I use these little devices to ramp through conditions of changing light during a timelapse. Many people swear by GB Timelapse; I don't like carrying around a computer when I'm already carrying a 60lb bag so I only use portable battery-powered Bulb-ramping devices.

Promote Controller

Depending on whom you ask, this device can be quite frustrating to setup and use, but once you figure it out it performs remarkably well. Most of my issues stemmed from faulty early firmware, which I only recently updated to version 3.2. According to Promote tech support, earlier versions had bugs in bulb ramping. This was evident to me in the form of flicker caused by uneven adjacent exposures.

After that obstacle was out of the way, the only main hindrance to learning the Promote to me was wrapping my head around the way it's engineers require the user to set long exposures at the start or finish of a timelapse. Setting the start/end exposure time to very long values like 4 minutes is very counter intuitive, but if you have the setup options set correctly it should do what you want it to after you practice many times and get used to the way it works.

First you should set up the following options in the setup menu. These parameters are for a Canon 5D Mark III body. Settings are (in parenthesis) and explanation are [in brackets]. MAKE SURE YOU UPDATE YOUR FIRMWARE!!!

Setup Options

#2 - Use a separate cable for shutter release: (Yes) [I'm not sure why you need to have a separate shutter cable, unlike the Timelapse + which is 100% USB control. Maybe it achieves greater sync with the PC terminal?]
#3 - Shutter cable frame delay (off)
#4 - USB Cable delay: (100ms)
#5 - Time-lapse exposure setting mode: Arbitrary (Bulb Mode)
#6 - Enable TL Schedule: (No)
#9 - Enable 1/3 EV ISO steps: (Yes) [also make sure you have this set in camera]
#10 - Bulb ramping live mods across (20 frames) [change this depending on how gradual you want changes to be applied and what your interval is]
#11 - Keep Bulb ramping length on start time change: (Yes)
#12- Enable Advanced bulb ramping: (Yes) [this is paramount to access all the other settings and the advanced BR screen]
#13 - Lowest ISO for advanced Bulb ramping (50) [This extra stop gives you more flexibility and extends your bramp time, make sure to set it in camera first]
#14 - Highest Auto ISO for Adv. Bulb ramping: (3200) [I can knock down noise at this ISO, while you can go higher I prefer to try to use fast glass and keep some information in the shadows]
#15 -Force ISO ramp down for short exposures: (Yes)
#16 - Limit longest exposure (30" or interval) [this is crucial because of the way the Promote works - this determines the upper time limit of your exposure at your highest ISO even though you may have it set to 4 minutes or something arbitrarily long. Remember the rule of 500 and how time / focal length determines whether you get star streaks or dots]
#17 - Bulb ramping long exposure limit mode (Hard - never exceed) [Again, keeping this at hard ensures you won't start to get star trails in your timelapse]
#18 - Auto bulb ramping interval extension: (Yes) [This will ramp your interval if, for example, you start before sunrise at 1/20th every 4 seconds and want to end at 30" every 32 seconds in three hours]
#19 - Bulb ramping live mod step size: (0.05 EV) [when you step the ramping up or down this setting provides the granularity control over the steps]
#20 - Bulb ramping interval measured as: (Exp start - exp start) [ This is another critical setting in terms of how you think of an "interval" versus a "shot cycle." The above setting makes the interval the total length of time from shutter open to the next shutter open, which is shutter + interval."]
#21 - Bulb ramp / HDR Image buffer time: (400ms)
#22 - Shutter close delay safety margin; (normal)
#23 - Shutter close delay Calibrate: (41ms) [Make sure you do this at least three or four times for each camera body you use. This setting seemed to be a good average for the 5D III]

Promote Settings - A Day to Night Bulb-Ramped Timelapse

The following steps are for a day to night timelapse, starting at or just before sunset, with NO ND filters used, and ending 1 hour past astronomical twilight. I started at 1/15th of a second at ISO 50 and ended up three hours later at 30 seconds at ISO 3200. Obviously you will need to tailor these settings to your specific conditions. Use an app like the Photographer's Ephemeris to plan for when to start ramping and how much to ramp.

I have ND filters, but I rarely choose to use them while bulb ramping since I am of the mentality that cameras are best left alone during timelapses so as to not inadvertently bump them and cause jumps in the resultant video.

1. Establish your composition. Lock down your tripod ball head (you should be using a ball head if you aren't!)

2. Consider whether you want to apply graduated ND filters, but remember that you won't be able to take them off!

3. Set your start exposure in M mode

4. Try to shoot wide open (smallest f-stop, largest diameter aperture). If you need to stop down for depth of field, or to drag your shutter, use the DOF-preview and lens-twist method if not using a manual aperture lens.

5. Take a test shot or four. Look at your histogram. It should be slightly right-justified (Expose to the Right). Your goal with Bulb ramping is to keep the histogram as much in the center as possible without letting your frame get too dark or too bright

6. CHECK YOUR FOCUS - I like to use Live View at 5x or 10x to do this

7. Be careful not to dislodge your lens if you twisted it halfway off

8. Connect the Promote - Bramp assist cable via PC hotshoe adapter, N3 shutter cable, and USB cable to your camera. Make sure you have the right end to the Promote - it has a "P" on it at the end.

9. Ensure setup options in Promote and on camera are set as above

10. Make sure you camera is in M mode, and that the camera is set at the ISO and shutter speed you want to START the timelapse at (ISO 50 / 1/15th")

11. Take your camera out of Live View! This was the main source of frustration for me in learning how to use this device - the PC sync does not work properly while in Live View, and thus neither will bramping with the Promote or ANY device.

12. Take a few test shots, and CHECK YOUR FOCUS. Nothing makes me more mad than blowing a shot because I forgot to double and triple check my focus. Make sure all your tripod clamps, ball-head knobs are all tight.

13. Pick up the Promote, and enter the Bulb-Ramping menu, you should see this screen:

14. Setup as follows:
--Start Tv (1/15th") [This should match your test shots]
--Each (15 seconds) [You can make this much smaller, the Promote will ramp up the interval depending on whether you set Setup #18]
--Begin Ramp in (01h00m) [Or, start ramping now depending on how close you are to the begining of dusk/twilight]
--End exposure value (32m - yes, 32 minutes) [This is completely counter intuitive to me - but you need to put in a value WAY beyond what you actually want your shot to end with. It was suggested to me by the Promote staff that this be the equivalent of a shot made at the lowest of your ISO settings (ISO 50). Surely it would make more sense to allow the user to input the actual end setting and have their b-ramping algorithm calculate the curve that way. Maybe a future firmware update will address this issue].
--In (02h44m) [This is the time you want the Promote to stop bramping and continue the timelapse with the end exposure parameters.]
--Finish seq in (03h44m) [This is the time the timelapse will stop shooting.]

18. Now you need to monitor your camera's histogram through your timelapse, and make any adjustments to the ramping rate (as setup by you in Setup #19, above). Press up / down to adjust the ramping rate, spread over the # of frames you chose in Setup #20 (we set it at 20 frames). You can also press left and right to adjust the ramping start time (corresponds to setup #).

That's it. Be prepared to try this many times, practice in your backyard or a nearby park so that you have your technique dialed when the time comes and you are at an epic location and only have one shot.

Here's a sunrise example of a well-executed Bramp. In post, I ramped the development parameters in LR TImelapse (exposure and WB) but I did not have to deflicker because the Promote did an excellent job.

Update February 2015- I have been having some issues with my Promote misfiring in the middle of a ramp in that adjacent exposures are jumping up/down and causing flicker. It's not pervasive, and it's not exactly repeatable. I updated the firmware to 3.2 per instructions form Promote staff and on the first test it seemed to solve the problem. More testing will take place in the coming weeks.